It is known that a subject presenting an injured posterior cruciate ligament, or one which is hyperextended as a result of a previous surgical operation, needs to use a knee brace designed to ensure the function of a hinged restraint between the femur and tibia, supporting stress that would otherwise be damaging for the ligament.
The knee brace usually consists of a rigid frame enclosing the knee in order to ensure an adequate support designed to prevent stress on the ligament when the injured and/or convalescing subject is walking.
The frame comprises means of restraint to the femur and to the tibia close to the knee and a structure connecting these means with a hinged coupling positioned at the level of the knee.
The knee brace frame comprises uprights, positioned laterally with respect to the femur and the tibia, connected by respective articulated joints generally equipped with 4 pivots designed to ensure excellent mobility thanks to the presence of multiple centres of rotation.
To ensure sufficient freedom of movement of the limb, the frame develops almost exclusively at the sides of the knee in order to allow correct reciprocal oscillation between the femur and the tibia.
The means of restraint usually consist of half rings enclosing both the femur and the tibia of the injured person.
The four-pivot articulated joints are used to ensure the hinged connection of the parts of the frame fixed to the femur and the tibia, extending during flexion of the limb and tending to become shorter when the limb is extended.
The risk of movements of the knee brace and of its slipping downwards is thus considerably reduced.
One disadvantage is represented by the fact that such knee braces will improbably allow certain and controllable angular movements, often making it necessary to resort to other ortheses.
It is also known that, depending on the severity of the injury, different people require different degrees of angular movement freedom.
If the possibilities of movement are too limited, the ligaments tend to become even stiffer, while excessive angular movements could further impair the functioning of the already damaged ligaments.